This stage one TRIP application will enable a phase II clinical trial of a new therapy to treat sickle cell disease (SCD) in two years. The basis of our proposal is our recent discovery that invariant NKT (iNKT) cells contribute importantly to tissue inflammation and injury in SCD mice. These cells are increased in number and activated in the blood of patients with SCD. Adenosine A2A receptors (A2AR) are highly expressed on iNKT cells and A2A agonists inhibit iNKT cell activation and reduce tissue damage in SCD mice. We hypothesize that A2A agonists will reduce inflammatory biomarkers in patient blood and reduce the duration and severity of painful SCD crises. We will use the A2A agonist, Lexiscan, that is clinically approved as a pharmacological stress agent, to conduct pilot safety and biomarker studies. In addition we will evaluate in mice additional anti-iNKT cell drug candidates that can be tested as alternatives to Lexiscan in subsequent clinical studies. We have assembled an expert team of clinical and basic investigators from three institutions. These include the Co-PI, David Nathan, M.D., a thought leader in SCD treatment who originated hydroxyurea therapy;and four other clinician scientists who direct adult and juvenile SCD clinics that will provide patients for these studies at Washington U., or Harvard-affiliated hospitals: Drs Joshua Field, Michael DeBaun, Maureen Okam and Mathew Heeney. The analysis of human blood for biomarkers will be conducted at the La Jolla Institute of Allergy and Immunology (LIAI) using cutting-edge flow cytometric techniques and overseen by the Basic Co-PI, Joel Linden, PhD, who discovered that iNKT cells exacerbate tissue injury in SCD mice and that iNKT cells are inhibited by A2A agonists. Co-investigators who will help evaluate iNKT cell function are two of the world's leading authorities on NKT cells, Drs. Mitch Kronenberg of LIAI and Mark Exley or Harvard. The aims for this stage I TRIP are summarized as follows: Preclinical studies: Aim 1 is to determine the optimal dose and duration of Lexiscan needed to reduce liver and lung inflammation and injury and reduce leukocyte activation in NY1DD (SCD) mice;Aim 2 is to evaluate anti-iNKTCR antibodies and novel glycolipid antagonists of iNKT receptors to determine if they are therapeutic candidates that can reduce tissue injury in SCD mice. Preliminary SCD clinical studies: Aim 3 is to conduct a small dose escalation study with Lexiscan infused for 12 h to determine the maximal tolerated dose (MTA) in SCD patients;Aim 4 is to evaluate the MTD for safety during infusion for 24 h;Aim 5 is to evaluate the MTD for safety in adult and juvenile patients during painful crises. During these studies we also will examine biomarkers of inflammation in the blood of patients. The primary goal of this stage one TRIP proposal is to prepare for a phase 2 clinical trial of Lexiscan for sickle cell painful crisis. Secondary goals are to prepare for a clinical trial of Lexiscan for acute chest syndrome, and to ready anti-iNKT cell receptor antibodies and glypolipid antagonists for future clinical evaluation in SCD. PUBLIC HEALTH RELEVANCE: Sickle cell disease (SCD) is the most common genetic blood disorder in the United States, affecting about 80,000 people (1 of every 600 African Americans). It causes short life span, pain and multi-organ failure. We have discovered a new anti-inflammatory approach to effectively treat SCD in mice and we plan to evaluate this new therapy in patients with SCD.